U.S. patent application number 13/250356 was filed with the patent office on 2013-04-04 for optimization of nfc tag for different battery levels.
The applicant listed for this patent is Mohamed Awad, Steven Hall, Theodore Trost. Invention is credited to Mohamed Awad, Steven Hall, Theodore Trost.
Application Number | 20130084803 13/250356 |
Document ID | / |
Family ID | 47993016 |
Filed Date | 2013-04-04 |
United States Patent
Application |
20130084803 |
Kind Code |
A1 |
Hall; Steven ; et
al. |
April 4, 2013 |
Optimization of NFC Tag For Different Battery Levels
Abstract
A mobile communication device has a processor, a radio, a near
field communication (NFC) device, a battery, and memory for storing
data. The power level of the battery is measured. When the measured
power level is above a first predetermined level, power is provided
to the radio to allow communication. Sufficient power is provided
to operate the NFC device as a reader and a tag. When the measured
power level of the battery falls below the first predetermined
level, battery power to the radio is shut off. Sufficient power is
maintained to the NFL device to allow it to operate only as a tag.
Sufficient power is maintained to the memory to retain the data
stored in the memory. When the measured power level of the battery
falls below a second predetermined level, the NFC device is
required to harvest all of its power from the field.
Inventors: |
Hall; Steven; (Olivenhain,
CA) ; Awad; Mohamed; (Ladera Ranch, CA) ;
Trost; Theodore; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hall; Steven
Awad; Mohamed
Trost; Theodore |
Olivenhain
Ladera Ranch
San Diego |
CA
CA
CA |
US
US
US |
|
|
Family ID: |
47993016 |
Appl. No.: |
13/250356 |
Filed: |
September 30, 2011 |
Current U.S.
Class: |
455/41.1 |
Current CPC
Class: |
Y02D 30/70 20200801;
H04W 52/028 20130101; H04W 52/0277 20130101; Y02D 70/42 20180101;
Y02D 70/22 20180101; H04W 24/02 20130101; H04B 5/0037 20130101;
H04B 5/0075 20130101; Y02D 70/166 20180101; H04W 4/80 20180201 |
Class at
Publication: |
455/41.1 |
International
Class: |
H04B 5/00 20060101
H04B005/00; H04W 24/00 20090101 H04W024/00 |
Claims
1. A method of controlling the operation of a mobile communication
device having a processor, a radio coupled to the processor that
enables wireless communication, a near field communication (NFC)
device coupled to the processor, a battery coupled to the processor
and the NFC device, and memory for storing data coupled to the NFC
device and the battery, comprising: measuring the power level of
the battery, wherein when the measured power level of the battery
is above a first predetermined level, providing power to the radio
to allow communication and providing sufficient power to the NFC
device to enable the NFC device to operate as a reader and a tag;
when the measured power level of the battery falls below the first
predetermined level, shutting off battery power to the radio to
disable the radio, maintaining sufficient power to the NFC device
to allow the NFC device to operate only as a tag, and maintaining
sufficient power to the memory to retain data stored in the memory;
and requiring the NFC device to operate only as a tag and to
harvest all of its power from a field when the measured power level
of the battery falls below a second predetermined level lower than
the first predetermined level.
2. The method of claim 1, further comprising: requiring the memory
to harvest all of its power from the field when the measured power
level of the battery falls below the second predetermined
level.
3. The method of claim 1, further comprising: maintaining
sufficient power to the memory to retain the data stored in the
memory while requiring the NFC device to harvest all of its power
from the field when the measured power level of the battery falls
below a third predetermined level lower than the second
predetermined level.
4. The method of claim 1, further comprising: determining the
number of transactions made with the mobile communication device
and transitioning from one power level to a second, lower power
level as a function of the number of transactions determined.
5. The method of claim 1, further comprising: determining the
length of time that the mobile communication device has been on and
transitioning from one power level to a second, lower power level
as a function of the determined length of time.
6. The method of claim 1, further comprising: determining the
number of data bits that have been transferred between the NFC
device and an external tag or reader during a given period of time
and transitioning from one power level to a second, lower power
level as a function of the determined number of bits.
7. A mobile communication device, comprising: a central processing
unit (CPU); a battery having multiple power levels coupled to the
CPU, the battery power levels being measured by the CPU; a radio
coupled to the CPU to enable the mobile communication device to
conduct wireless communications and coupled to the battery to draw
power from the battery when battery power is above a first
predetermined level; a near field communication (NEC) device
coupled to the CPU and the battery and operable as a reader and a
tag when battery power is above the first predetermined level;
wherein when the battery power falls below the first predetermined
level, power to the radio is shut off and the NFC device is
operable only as a tag; and a memory coupled to the NFC device and
the battery and drawing sufficient power from the battery when the
battery power falls below the first predetermined level to retain
data stored in the memory; and wherein when the measured battery
power falls below a second predetermined level lower than the first
predetermined level, the NFC device harvests all of its power from
the field.
8. The mobile communication device of claim 7, wherein: the memory
harvests all of its power from the field when the power level falls
below the second predetermined level.
9. The mobile communication device of claim 7, wherein: the memory
draws power from the battery when the measured battery power falls
below a third predetermined level lower than the second
predetermined level to retain data stored in the memory; and the
NFC device harvests all of its power from the field when measured
battery power falls below the third predetermined level.
10. The mobile communication device of claim 7, wherein: the
battery is transitioned from one power level to a second, lower
power level as a function of the number of transactions made with
the mobile communication device.
11. The mobile communication device of claim 7, wherein: the
battery is transitioned from one power level to a second, lower
power level as a function of the length of time that the mobile
communication device has been on.
12. The mobile communication device of claim 7, wherein: the
battery is transitioned from one power level to a second, lower
power level as a function of the number of data bits that have been
transferred between the NFC device and an external tag or reader
during a given period of time.
13. An article of manufacture including a non-volatile computer
readable medium having computer program logic stored thereon that,
when executed by a computing device, cause the computing device to
perform battery saving operations in a mobile communication device
having a processor, a radio coupled to the processor that enables
wireless communication, a near field communication (NFC) device
coupled to the processor, a battery coupled to the processor and
the NFC device, and memory for storing data coupled to the NFC
device and the battery, comprising: measuring the power level of
the battery, wherein when the measured power level of the battery
is above a first predetermined level, providing power to the radio
to allow communication and providing sufficient power to the NFC
device to enable the NFC device to operate as a reader and a tag;
when the measured power level of the battery falls below the first
predetermined level, shutting off battery power to the radio to
disable the radio, maintaining sufficient power to the NFC device
to allow the NFC device to operate only as a tag, and maintaining
sufficient power to the memory to retain data stored in the memory;
and requiring the NFC device to operate only as a tag and to
harvest all of its power from a field when the measured power level
of the battery falls below a second predetermined level lower than
the first predetermined level.
14. The article of manufacture according to claim 13, wherein the
computer program logic, when executed by the computing device,
cause the computing device to perform the following additional
operations, including: requiring the memory to harvest all of its
power from the field when the measured power level of the battery
falls below the second predetermined level.
15. The article of manufacture according to claim 13, wherein the
computer program logic, when executed by the computing device,
cause the computing device to perform the following additional
operations, including: maintaining sufficient power to the memory
to retain the data stored in the memory while requiring the NEC
device to harvest all of its power from the field when the measured
power level of the battery falls below a third predetermined level
lower than the second predetermined level.
16. The article of manufacture according to claim 13, wherein the
computer program logic, when executed by the computing device,
cause the computing device to perform the following additional
operations, including: determining the number of transactions made
with the mobile communication device and transitioning from one
power level to a second, lower power level as a function of the
number of transactions determined.
17. The article of manufacture according to claim 13, wherein the
computer program logic, when executed by the computing device,
cause the computing device to perform the following additional
operations, including: determining the length of time that the
mobile communication device has been on and transitioning from one
power level to a secord, lower power level as a function of the
determined length of time.
18. The article of manufacture according to claim 13, wherein the
computer program logic, when executed by the computing device,
cause the computing device to perform the following additional
operations, including: determining the number of data bits that
have been transferred between the NFC device and an external tag or
reader during a given period of time and transitioning from one
power level to a second, lower power level as a function of the
determined number of bits.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The present invention relates generally to near field
communications.
[0003] 2. Background ART
[0004] Near field communication, or NFC, is a set of short-range
wireless technologies, typically requiring a distance of 4 cm or
less. NFC generally operates at 13.56 MHz and at rates ranging from
about 106 kbit/s to 848 kbit/s. NFC generally involves a reader (or
initiator) and a tag (or target); the reader actively generates an
RF field that can power a passive tag. This enables NFC tags to be
configured so as to have very simple form factors such as tags,
stickers, key fobs, or cards that do not require batteries. NFC
peer-to-peer communication is of course possible, where both
devices are powered. Devices that contain both reader and tag
capabilities are often called controllers.
[0005] Near field communications (NFC) devices can be integrated
into mobile devices, such as smartphones, for example, to
facilitate the use of these mobile devices in conducting daily
transactions. For example, instead of carrying numerous credit
cards, the credit information provided by these credit cards could
be stored onto a NFC device. The NFC device is simply tapped to a
credit card terminal to relay the credit information to it to
complete a transaction. As another example, ticket writing systems,
such as those used in bus and train terminals, may simply write
ticket fare information onto the NFC device instead of providing a
paper ticket to a passenger. The passenger simply taps the NFC
device to a reader to ride the bus or the train without the use of
a paper ticket.
[0006] Generally, NFC requires that NFC devices be present within a
relatively close proximity to each other so that their
corresponding magnetic fields can exchange information. Typically,
a first NFC device transmits or generates a magnetic field
modulated with the information, such as the credit information or
the ticket fare information. This magnetic field inductively
couples onto a second NFC device that is proximate to the first NFC
device. The second NFC device may respond to the first NFC device
by transmitting or generating its own modulated magnetic field and
inductively coupling this magnetic field to the first NFC
device.
[0007] Mobile communication devices, such as smartphones, tablet
computers, notebook computers, and the like, are generally battery
powered. The battery in these devices has a finite life before it
requires recharging. Manufacturers of mobile devices that
incorporate NFC devices generally want them to be able to operate
as card emulators. In card emulation mode, the mobile device can
take the place of a credit or debit card to make purchases or
perform other financial tasks that cards can normally accomplish.
In addition, in card emulation mode, the mobile device may be used
to access transportation systems, allowing a user to enter and/or
exit a subway or bus system, for example. It is desirable to
incorporate features into the mobile communication devices that
will allow them to operate in card emulation mode even when they
cannot be used to make or receive calls or access the Internet.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
[0008] The accompanying drawings, which are incorporated herein and
form a part of the specification, illustrate the present invention
and, together with the description, further serve to explain the
principles of the invention and to enable a person skilled in the
pertinent art to make and use the invention.
[0009] FIG. 1 shows a block diagram of an NFC environment.
[0010] FIG. 2 shows an exemplary embodiment of a mobile
communication device containing a NFC device as described
herein.
[0011] FIG. 3 is a power state diagram of the mobile communication
device described herein.
[0012] FIG. 4 is a chart of battery power over time.
[0013] The present invention will be described with reference to
the accompanying drawings. Generally, the drawing in which an
element first appears is typically indicated by the leftmost
digit(s) in the corresponding reference number.
DETAILED DESCRIPTION
[0014] The following Detailed Description refers to accompanying
drawings to illustrate exemplary embodiments consistent with the
invention. References in the Detailed Description to "one exemplary
embodiment," "an exemplary embodiment," "an example exemplary
embodiment," etc., indicate that the exemplary embodiment described
may include a particular feature, structure, or characteristic, but
every exemplary embodiment may not necessarily include the
particular feature, structure, or characteristic. Moreover, such
phrases are not necessarily referring to the same exemplary
embodiment. Further, when a particular feature, structure, or
characteristic is described in connection with an exemplary
embodiment, it is within the knowledge of those skilled in the
relevant art(s) to affect such feature, structure, or
characteristic in connection with other exemplary embodiments
whether or not explicitly described.
[0015] The exemplary embodiments described herein are provided for
illustrative purposes, and are not limiting. Other exemplary
embodiments are possible, and modifications may be made to the
exemplary embodiments within the spirit and scope of the invention.
Therefore, the Detailed Description is not meant to limit the
invention. Rather, the scope of the invention is defined only in
accordance with the following claims and their equivalents.
[0016] Embodiments of the invention may be implemented in hardware,
firmware, software, or any combination thereof. The following
Detailed Description of the exemplary embodiments will so fully
reveal the general nature of the invention that others can, by
applying knowledge of those skilled in relevant art(s), readily
modify and/or adapt for various applications such exemplary
embodiments, without undue experimentation, without departing from
the spirit and scope of the invention. Therefore, such adaptations
and modifications are intended to be within the meaning and
plurality of equivalents of the exemplary embodiments based upon
the teaching and guidance presented herein. It is to be understood
that the phraseology or terminology herein is for the purpose of
description and not of limitation, such that the terminology or
phraseology of the present specification is to be interpreted by
those skilled in relevant art(s) in light of the teachings
herein.
[0017] Although, the description of the present invention is to be
described in terms of NFC, those skilled in the relevant art(s)
will recognize that the present invention may be applicable to
other communications that use the near field and/or the far field
without departing from the spirit and scope of the present
invention. For example, although the present invention is to be
described using NFC capable communication devices, those skilled in
the relevant art(s) will recognize that functions of these NFC
capable communication devices may be applicable to other
communications devices that use the near field and/or the far field
without departing from the spirit and scope of the present
invention.
[0018] FIG. 1 illustrates a block diagram of a NFC environment 100
according to an exemplary embodiment. NFC environment 100 provides
wireless communication of information among a first NFC device 102
and a second NFC device 104 that are closely proximate to each
other (typically between 0 cm and 4 cm spacing). The information
may include one or more commands to be executed by the first NFC
device 102 and/or the second NFC device 104, data from one or more
data storage devices that is to be transferred to the first NFC
device 102 and/or the second NFC device 104, or any combination
thereof. The data storage devices may include one or more
contactless transponders, one or more contactless tags, one or more
contactless smartcards, or any other machine-readable media that
will be apparent to those skilled in the relevant art(s) without
departing from the spirit and scope of the invention, or any
combination thereof. The other machine-readable media may include,
but are not limited to, read only memory (ROM), random access
memory (RAM), magnetic disk storage media, optical storage media,
flash memory devices, electrical, optical, acoustical or other
forms of propagated signals such as carrier waves, infrared
signals, digital signals to provide some examples.
[0019] NFC devices 102 and 104 may be any of three types of
devices. One type is a tag, or target. A tag is passive. A tag
contains data or commands. When brought into communication with
another device, the tag transfers data and/or commands to the
second device. As one example, a tag may be an ID card that permits
access to a building when the data stored on the tag is read. A
second type is a reader, or initiator. A reader generates an
electromagnetic field which is modulated by a tag. An example of a
reader may be the unit mounted on the building wall that reads the
information stored in the tag. The reader reads data stored on the
tag and may take action based on the received information. A
controller is a device that incorporates features of both a tag and
a reader. A controller typically has more "intelligence" than a
tag. That is, a controller may handle more computational and
operational functions than a tag. A controller may act as a tag, or
a reader, or both. For purposes of the present disclosure, a tag, a
reader, and a controller will be referred to herein individually
and collectively as a "NFC device."
[0020] The first NFC device 102 and/or the second NFC device 104
may be implemented as a standalone or a discrete device or may be
incorporated within or coupled to larger electrical devices or host
devices such as mobile telephones, portable computing devices,
other computing devices such as personal, laptop, tablet, or
desktop computers, computer peripherals such as printers, portable
audio and/or video players, television receivers, a payment system,
ticket writing systems such as parking ticketing systems, bus
ticketing systems, train ticketing systems or entrance ticketing
systems to provide some examples, or in ticket reading systems,
toys, games, posters, packaging, advertising materials, product
inventory checking systems and/or any other suitable electronic
device that will be apparent to those skilled in the relevant
art(s) without departing from the spirit and scope of the
invention.
[0021] The first NFC device 102 and/or the second NFC device 104
interact with each other to exchange information such as data
and/or one or more commands to be executed by the first NFC device
102 and/or the second NFC device 104. Each NFC device 102 and 104
contains an antenna 106 and 108, respectively, to enable NFC
devices 102 and 104 to communicate with each other. One example of
such communications is a peer (P2P) communications mode or a
reader/writer (R/W) communications mode. In the P2P communications
mode, the first NFC device 102 and the second NFC device 104 may be
configured to operate according to an active communications mode
and/or a passive communications mode. The first NFC device 102
modulates first information onto a first carrier wave, referred to
as a modulated data communication, and generates a first magnetic
field by applying the modulated data communications to the first
antenna 106 to provide a first data communications 110. The first
NFC device 102 ceases to generate the first magnetic field after
transferring the first information to the second NFC device 104 in
the active communications mode via the second antenna 108.
Alternatively, in the passive communications mode, the first NFC
device 102 continues to apply the first carrier wave without the
first information, referred to as an unmodulated data
communication, to continue to provide the first data communications
110 once the first information has been transferred to the second
NFC device 104.
[0022] In the P2P communication mode, the first NFC device 102 is
sufficiently closely proximate to the second NFC device 104 that
the first data communications 110 is inductively coupled onto the
second antenna 108 of the second NFC device 104. The second NFC
device 104 demodulates the first data communications 110 to recover
the first information. The second NFC device 104 may respond to the
first information by modulating second information onto a second
carrier wave and generating a second magnetic field by applying
this modulated data communications to the second antenna 108 to
provide a second modulated data communications 112 in the active
communications mode. Alternatively, the second NFC device 104 may
respond to the first information by modulating the first carrier
wave that is inductively coupled onto the second antenna 108 with
the second information to provide the second modulated data
communications 112 in the passive communications mode.
[0023] In the R/W communications mode, the first NFC device 102 is
configured to operate in an initiator, or reader, mode and the
second NFC device 102 is configured to operate in a target, or tag,
mode. This example is not limiting. Those skilled in the relevant
art(s) will recognize that the first NFC device 102 may be
configured to operate in the tag mode and the second NFC device 104
may be configured to operate in the reader mode in accordance with
the teachings herein without departing from the spirit and scope of
the present invention. The first NFC device 102 modulates the first
information onto the first carrier wave and generates the first
magnetic field by applying the modulated data communications to the
first antenna 106 to provide the first data communications 110. The
first NFC device 102 continues to apply the first carrier wave
without the first information to continue to provide the first data
communications 110 once the first information has been transferred
to the second NFC device 104. The first NFC device 102 is
sufficiently closely proximate to the second NFC device 104 that
the first data communications 110 is inductively coupled onto the
second antenna 108 of the second NFC device 104.
[0024] The second NFC device 104 derives or harvests power from the
first data communications 110 to recover, to process, and/or to
provide a response to the first information. The second NFC device
104 demodulates the first data communications 110 to recover the
first information. The second NFC device 104 processes the first
information. The second NFC device 104 may respond to the first
information by modulating the second information onto the second
carrier wave and generating the second magnetic field by applying
this modulated data communications to the second antenna 108 to
provide the second modulated data communications 112.
[0025] Further operations of the first NFC device 102 and/or the
second NFC device 104 may be described in International Standard
ISO/IE 18092:2004(E), "Information Technology--Telecommunications
and Information Exchange Between Systems--Near Field
Communication--Interface and Protocol (NFCIP-1)," published on Apr.
1, 2004 and International Standard ISO/IE 21481:2005(E),
"Information Technology--Telecommunications and Information
Exchange Between Systems--Near Field Communication--Interface and
Protocol-2 (NFCIP-2)," published on Jan. 15, 2005, each of which is
incorporated by reference herein in its entirety.
[0026] The present disclosure is directed to the most efficient use
of battery power in a mobile communication device which operates in
card emulation mode. Disclosed embodiments find particular utility
in situations where it is desired to optimize battery life for the
NFC device. Handset carriers (e.g., mobile phone providers) desire
to have mobile devices that have various power levels of operation,
from full power that allows the user to make calls, access the
Internet, send and receive e-mail, send and receive text messages,
etc., down to a minimal power state that maintains memory and still
allows the mobile device to emulate a card, such as, but not
limited to, a credit card, a debit card, a transportation system
access card, etc. The operations described herein can be performed
by hardware, software, or a combination of hardware and
software.
[0027] FIG. 2 shows a block diagram of a mobile device 200 of the
type to which this invention is directed. Mobile device 200, such
as a smartphone or the like, contains a host 202, which includes a
Central Processing Unit (CPU) or the "brains" of mobile device 200.
Host 202 is electrically coupled to a NFC controller and radio 204.
NFC controller 204 transmits and receives data via a NFC antenna
206 and the telecommunications circuitry of mobile device 200.
Together, NFC controller 204 and its associated NFC antenna 206
comprise a "NFC device." A battery 208 supplies power to all of the
electrical circuits, including, but not limited to CPU 202, the NFC
device, and the radio circuit. The NFC device monitors the power
levels of battery 208 and controls certain operations of the mobile
device based on the detected or measured battery power level, as
will be described in more detail below.
[0028] Mobile device 200 may also include one or more types of
memory. One type is a non-volatile memory device 210 that does not
require constant battery power to retain data. A second type is a
secure memory element 212 that is powered by battery 208 directly
or through the NFC device. Both non-volatile memory 210 and secure
memory element 212 can hold secure information, such as passwords,
credit and/or debit card numbers, transportation access numbers,
and the like. If mobile device 200 includes non-volatile memory 210
to store the secure information, there is no need for secure
element 212. If mobile device does not contain non-volatile memory
210, it will include a secure element (or "keep alive memory") 212,
which draws very little power from battery 208. Secure element 212
replaces non-volatile memory 210 and contains the secure
information or "personalized data" of the user. If mobile device
200 contains non-volatile memory 210, there is essentially no
reason to include low power mode secure element 212.
[0029] The use of secure element 212 is of particular interest to
mobile phone manufacturers. Secure element 212 draws very little
power from battery 208 (on the order of several .mu.amps). Even
when battery power is so low that mobile device 200 is effectively
turned off and the NFC device must operate in field power mode,
there will likely be sufficient battery power available to maintain
power to secure element 212 for several days and keep the
information stored in secure element 212 alive until the user can
recharge the battery. The "keep alive" memory or secure element 212
can be used in place of non-volatile memory 210 at a fraction of
the cost of non-volatile memory 210.
[0030] FIG. 3 shows a diagram of the power states of the mobile
device utilizing the power management features of this invention.
State 302 represents a fully battery powered mode, where the mobile
device is able to make and receive calls, "surf" the Internet, send
and receive e-mails, etc. The NFC device or host 202 monitors
battery power levels. When operating in fully battery powered mode,
the NFC device can act as a reader or a tag. In this state, the NFC
device can operate at a greater distance from an external reader or
the reader can operate with less power than if the NFC device is
operating only as a tag.
[0031] In one example, The NFC device in mobile device 200 is
capable of operating as a reader and communicating with a tag. For
example, a movie poster may have a NFC tag attached to it. When The
NFC device in mobile device 200 is held in contact or close
communication with the NFC tag on the poster, the tag will harvest
power from The NFC device and communicate the information contained
in the tag to mobile device host 202. Typically, this information
could be in the form of a schedule of movie theaters and times; or
the information could be in the form of an Internet address (or
URL) to provide more information about the movie. If there is
sufficient battery power available to permit access to the
Internet, mobile device 200 may then be taken to the website
associated with that URL. Alternatively, if there is insufficient
battery power available to access the Internet, The NFC device can
store the URL in local memory 210 or 212 in mobile device 200. The
stored URL can then be accessed at a later time when more battery
power has been restored (e.g., by recharging the battery or by
replacing the discharged battery with a fully charged battery). In
another non-limiting example, a tag could be attached to a bus stop
sign and provide information about bus schedules and routes
associated with that stop.
[0032] Over time, battery 208 loses power, through a combination of
usage and leakage. At a certain point, when host CPU 202 (i.e., the
"brains") of mobile device 200 determines that there is in
insufficient power to support communications applications (e.g.,
voice, Internet, e-mail, etc.), it will shut off all communications
functions. For example, below a predetermined battery power level,
mobile device 200 typically will not be able to make or receive
phone calls, send or receive e-mail and/or text messages and/or
access the Internet. In this low power mode 304, battery 208
continues to provide power to the NFC device such that the NPC
device can act as a tag in a card emulation mode. In this low power
mode, the field need not be as strong as it must be in lower power
modes and the NFC device can operate over a greater range than in
the lower power modes.
[0033] The system has the ability to transition from one power mode
to another after a fixed number of transactions, such as the number
of phone calls made to or from the mobile device, the number of
times the user accesses the Internet with the mobile device, the
number of text messages sent or received by the mobile device, or
any other type of suitable measuring transaction that would be
apparent to one skilled in the relevant art. Alternatively, the
system (CPU 202 or NFC device) can determine when to transition to
a lower power mode as a function of the amount of time the mobile
device has been "on" and drawing power (as the "on" time has a
direct relationship to the amount of battery power that has been
used), or as a function of a count of the number of bits that have
been transferred between the NFC device and a reader (or tag).
[0034] As battery power further decreases, NFC controller 204 will
instruct host CPU 202 to transition mobile device 200 to a very low
power mode 306. In this mode, battery 208 provides enough power to
maintain secure element ("keep alive memory") 212 active. The data
in keep alive memory 212, called "personality data," is stored in
secure element 212 and may include secure information and the types
of credit cards for which mobile device 202 acts as a card
emulation device. All other power to the NFC device is harvested
from the field (i.e., supplied by a reader). The NFC device may act
as a tag, and communicate with a reader to transmit (e.g., credit
card) information to the reader. In this mode, battery 208 provides
power to memory 212 to keep the memory "alive." All other
functionality is provided by power harvested from the field. That
is, the NFC device draws its power from the field generated by a
reader. Usually battery 208 retains enough energy to power keep
alive memory 212 for up to several days, allowing time for the user
to recharge battery 208. The ability to use a secure element ("keep
alive memory") 212 is of interest to mobile device manufacturers,
since this type of device is less expensive than a non-volatile
memory 210, thereby allowing manufacturers to reduce the cost of
their devices.
[0035] If mobile device 200 contains non-volatile memory 210, there
is no need to have secure element 212. In that case, there is also
no need for mobile device 200 to use very low power mode 306.
Non-volatile memory retains the secure "personality data" even when
battery power has decreased to zero.
[0036] The last mode shown in FIG. 3 is a field power mode 308. In
this mode, battery 208 is fully discharged or may even have been
removed from mobile device 200. The NFC device acts as a tag and
harvests all of its power from the field. Non-volatile memory 210
harvests power from the field through the NFC device in a known
manner. If mobile device 200 does not contain non-volatile memory
210, it could not use field power mode 308. Since there is no
battery power at all available in this mode, secure "personality
data" would not be retained if only keep alive memory 212 were
available. Absent non-volatile memory 210, secure data is only
retained in secure element 212, which requires power at all times
to retain data.
[0037] FIG. 4 is a diagram of the power transition states against
battery power. Battery power is shown as a plot 402. The
fluctuation in power in the range between thresholds V.sub.4 and
V.sub.3 is primarily a function of battery usage of mobile device
200 when making and receiving calls, when accessing the Internet,
or when sending or receiving e-mails and/or text messages, and the
like. The range between thresholds V.sub.4 and V.sub.3 shows the
state in which there is sufficient battery power to make and
receive calls. This is fully powered mode 302. At some point,
battery power drops below the threshold necessary to maintain radio
(i.e., phone and/or Internet) communications. Host CPU 202 then
instructs the NFC device to enter low power mode 304. Below
threshold V.sub.3, host CPU 202 turns off the radio circuits in the
mobile device and communications are disabled. Below threshold
V.sub.3, the NFC device operates only as a tag. Between thresholds
V.sub.3 and V.sub.2, the system operates in low power mode 304.
Below threshold V.sub.2, mobile communication device 200 operates
in very low power mode 306 if it contains keep alive memory 212. In
this state, the battery provides only enough power to keep alive
data in memory 212. Typically, battery 208 can maintain keep alive
memory 212 active for up to several days, which should be long
enough for the user to recharge the battery.
[0038] If mobile communication device 200 does not contain keep
alive memory 212, but instead contains non-volatile memory 210, the
operating range between thresholds V.sub.2 and V.sub.1 may be done
away with, since non-volatile memory 210 does not require battery
power to retain data stored in it. At any rate, below threshold
V.sub.1, no power at all is supplied by battery 208. At this point,
battery 208 is either completely drained or has been removed. Below
threshold V.sub.1, mobile communication device 200 will operate
only as a NFC tag. In this state, mobile communication device 200
must contain non-volatile memory 210 in order for it to act in card
emulation mode. The NFC device must harvest all of its power from
the field, including the power needed to access data stored in
memory 210.
[0039] Embodiments have been described above with the aid of
functional building blocks illustrating the implementation of
specified functions and relationships thereof. The boundaries of
these functional building blocks have been arbitrarily defined
herein for the convenience of the description. Alternate boundaries
can be defined so long as the specified functions and relationships
thereof are appropriately performed.
[0040] The foregoing description of the specific embodiments will
so fully reveal the general nature of the invention that others
can, by applying knowledge within the skill of the art, readily
modify and/or adapt for various applications such specific
embodiments, without undue experimentation, without departing from
the general concept of the present invention. Therefore, such
adaptations and modifications are intended to be within the meaning
and range of equivalents of the disclosed embodiments, based on the
teaching and guidance presented herein. It is to be understood that
the phraseology or terminology herein is for the purpose of
description and not of limitation, such that the terminology or
phraseology of the present specification is to be interpreted by
the skilled artisan in light of the teachings and guidance.
[0041] The breadth and scope of embodiments of the present
invention should not be limited by any of the above-described
exemplary embodiments, but should be defined only in accordance
with the following claims and their equivalents.
* * * * *